Deadly fires show how northern state is becoming more...

1of65Fire fighters clear a downed tree from across Mt. Veeder Rd after flames from the Nuns fire moved through the Mt Veeder area in Napa on Oct. 11, 2017.Photo: Peter DaSilva, Special to The Chronicle

2of65A grove of trees near Trinity Road glows as it burns near a vineyard after a mandatory evacuation was called in the area of Glen Ellen, Calif., on Wednesday, Oct. 11, 2017. The Napa and Sonoma valleys continue to be under threat from several fires not yet under control and growing fears that strong winds might worsen the situation.Photo: Carlos Avila Gonzalez, The Chronicle

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4of65A water tanker truck to support fire crews overturned, killing the driver on Oakville Grade near Highway 29 on Monday, Oct. 16, 2017 in Oakville, CA.Photo: Paul Kuroda, Special to The Chronicle

5of65Fire along the ridge in Oakville being doused by helicopters on Monday, Oct. 16, 2017 in Oakville, CA.Photo: Paul Kuroda, Special to The Chronicle

6of65A large plume of smoke rises above the mountains between Napa and Sonoma, Calif., on Sunday, October 15, 2017.Photo: Scott Strazzante, The Chronicle

7of65Scott family members Melody (left), Jenna, 9, Olivia, 3, being held by Kaylee, 12, and Daniel, 9, at New Hope Baptist service at the DoubleTree hotel in Rohnert Park.Photo: Gabrielle Lurie / Gabrielle Lurie / The Chronicle

8of65Brittany Perry hands out a free ash sifter to a fire victim at Pacific Coast Custom Interiors in Santa Rosa, Calif., on Sunday, October 15, 2017.Photo: Scott Strazzante, The Chronicle

9of65From atop his truck parked along Highway 29, Marcos Barrera of Napa watches fires burn west of St. Helena, Calif., on Sunday, October 15, 2017.Photo: Scott Strazzante, The Chronicle

10of65After the mandatory fire evacuation order was lifted, 10-year-old twins Porter and Katie Lynch pause while riding their bikes on Cedar Street in Calistoga, Calif., on Sunday, October 15, 2017.Photo: Scott Strazzante, The Chronicle

11of65Caroll Niel leans on her husband, firefighter Tony Niel, in the motorhome where they are staying following the Tubbs fire on Friday, Oct. 13, 2017, in Forestville, Calif.Photo: Noah Berger / Special to The Chronicle

12of65Santa Rosa firefighter Tony Niel passes a portion of fence standing at his Mark West Estates home, which burned during the Tubbs fire, on Thursday, Oct. 12, 2017, in Santa Rosa.Photo: Noah Berger / Special to The Chronicle

15of65Statue at the Mondavi Winery and a groundsman mows lawn as fires burn on Monday, Oct. 16, 2017 in Oakville, CA.Photo: Paul Kuroda, Special to The Chronicle

16of65Josiah Gist (right) joins fellow Santa Cruz firefighters in using pool water in firefighting efforts at a large home that burned in The Ranch subdivision in Sonoma, Calif., on Saturday, October 14, 2017.Photo: Scott Strazzante, The Chronicle

17of65A firefighter walks through what remains of a large home that burned in The Ranch subdivision in Sonoma, Calif., on Saturday, October 14, 2017.Photo: Scott Strazzante, The Chronicle

18of65Three firefighters look at a large home that burned in The Ranch subdivision in Sonoma, Calif., on Saturday, October 14, 2017.Photo: Scott Strazzante, The Chronicle

20of65Smoke in the hills east of Sonoma, Calif., on Saturday, October 14, 2017.Photo: Scott Strazzante, The Chronicle

21of65The chimney is all that remains standing at a large home that burned in The Ranch subdivision in Sonoma, Calif., on Saturday, October 14, 2017.Photo: Scott Strazzante, The Chronicle

22of65Santa Cruz firefighters' Josiah Gist and Ian Adams carry a hose over the pool of a large home that burned in The Ranch subdivision in Sonoma, Calif., on Saturday, October 14, 2017.Photo: Scott Strazzante, The Chronicle

23of65Fire fighters work on putting out hotspots at a home off Lovall Rd in Sonoma, California, USA 14 Oct 2017.Photo: Peter DaSilva, Special to The Chronicle

24of65Gss main continues to burn at a home destroyed by flames early Saturday morning along the 1100 block of Castle Rd in Sonoma, California, USA 14 Oct 2017.Photo: Peter DaSilva, Special to The Chronicle

25of65A water tender sprays water along the roadside to put out hot spots along the 1100 block of Castle Rd in Sonoma, California, USA 14 Oct 2017.Photo: Peter DaSilva, Special to The Chronicle

26of65Sun rises behind burned out hillside east of the town of Sonoma, California, USA 14 Oct 2017.Photo: Peter DaSilva, Special to The Chronicle

27of65Fire fighters work on putting out hotspots in a garage at a home off Lovall Rd in Sonoma, California, USA 14 Oct 2017.Photo: Peter DaSilva, Special to The Chronicle

28of65Search and rescue worker rests on his car after looking through the rubble of a home on Millbrook Drive on Friday, Oct. 13, 2017, in Santa Rosa, Calif.Photo: Mason Trinca, Special to The Chronicle

29of65Search and rescue worker looks through the rubble of a home on Millbrook Drive on Friday, Oct. 13, 2017, in Santa Rosa, Calif.Photo: Mason Trinca, Special to The Chronicle

30of65Search and rescue workers dig the rubble of a home on Millbrook Drive on Friday, Oct. 13, 2017, in Santa Rosa, Calif. Rosa, Calif.Photo: Mason Trinca, Special to The Chronicle

31of65California Highway Patrol officer Tracy Ross (center) talks on the phone while assiting Tom Sours (left) of Napa, as he was trying to get to his home to pick up some items on Friday, October 13, 2017 in Napa, Calif.Photo: Lea Suzuki, The Chronicle

32of65Search and rescue workers search for Tubbs fire victims at Journey's End Mobile Home Park on Friday, Oct. 13, 2017, in Santa Rosa, Calif. According Sgt. Dave Thompson, in charge of search and rescue operations for the Sonoma County Sheriffs Office, crews have recovered another body at the site.Photo: Noah Berger, Special to The Chronicle

33of65Search and rescue workers from the Sonoma County Sheriffs Office search for Tubbs fire victims at Journey's End Mobile Home Park on Friday, Oct. 13, 2017, in Santa Rosa, Calif. According Sgt. Dave Thompson, in charge of search and rescue operations for the Sonoma County Sheriffs Office, crews have recovered another body at the site.Photo: Noah Berger, Special to The Chronicle

34of65Search and rescue workers use human remain detection dogs to search for Tubbs fire victims at Journey's End Mobile Home Park on Friday, Oct. 13, 2017, in Santa Rosa, Calif. According Sgt. Dave Thompson, in charge of search and rescue operations for the Sonoma County Sheriffs Office, crews have recovered another body at the site.Photo: Noah Berger, Special to The Chronicle

35of65A man shows a burnt paper after a wildfire moved through the area in Santa Rosa and Napa Valley in California, United States on October 13, 2017. Massive out-of-controls wildfires have claimed at least 31 people and destroyed 3,500 homes in Northern California as the deadliest in state history. (Photo by Tayfun Coskun/Anadolu Agency/Getty Images)Photo: Anadolu Agency/Getty Images

36of65The remains are seen after a wildfire moved through the area in Santa Rosa and Napa Valley in California, United States on October 13, 2017. Massive out-of-controls wildfires have claimed at least 31 people and destroyed 3,500 homes in Northern California as the deadliest in state history. (Photo by Tayfun Coskun/Anadolu Agency/Getty Images)Photo: Anadolu Agency/Getty Images

37of65Chrystal Couto holds a poster of her grandmother as Aaron Austin looks on in Santa Rosa, Calif. on Friday, Oct. 13, 2017. The couple from Redway, are searching for Couto's grandmother and her husband, who haven't been heard from since a wildfire tore through the older couple's Santa Rosa neighborhood. They are hanging flyers in evacuation centers with photos of the older couple. (AP Photo/Paul Elias)Photo: Paul Elias/AP

38of65Flowers mark the spot where their father died as Chuck and Mike (R) Rippey stand in the ruins of the house of 100-year-old Charles and 98-year-old Sara Rippey, who were killed in the Atlas Fire just after it began, on October 12, 2017 near Napa, California. Thousands homes have burned and two dozen people have been confirmed dead so far as numerous wildfires continue to spread in eight Northern California counties. (Photo by David McNew/Getty Images)Photo: David McNew/Getty Images

40of65In this Tuesday, Oct. 10, 2017, photo provided by Sam Brinkerhoff, his wife Monica Brinkerhoff takes a photo of her wedding ring that was found in the burned remains of her home in Santa Rosa, Calif. She had hoped to retrieve a passport from her fire-resistant safe, but that too was consumed by the flames. She wasn't prepared for what she did find, the couple's soot-covered engagement rings, with a pair of etched hearts still visible on one of the bands. (Sam Brinkerhoff via AP)Photo: Sam Brinkerhoff/AP

41of65Firefighters try to extinguish a house fire during the Tubbs Fire on October 12, 2017 near Calistoga, California. At least thirty one people have died in wildfires that have burned tens of thousands of acres and destroyed over 3,500 homes and businesses in several Northern California counties. (Photo by Justin Sullivan/Getty Images)Photo: Justin Sullivan/Getty Images

42of65A CalFire chief runs past burning grass during a firing operation while battling the Tubbs Fire on October 12, 2017 near Calistoga, California. At least thirty one people have died in wildfires that have burned tens of thousands of acres and destroyed over 3,500 homes and businesses in several Northern California counties. (Photo by Justin Sullivan/Getty Images)Photo: Justin Sullivan/Getty Images

43of65Two firefighters watch for spot fires Friday, Oct. 13, 2017, near Calistoga, Calif. Firefighters gained some ground on a blaze burning in the heart of California's wine country but face another tough day ahead with low humidity and high winds expected to return. (AP Photo/Jae C. Hong)Photo: Jae C. Hong, Associated Press

44of65A CalFire firefighter uses a hand tool as he monitors a firing operation while battling the Tubbs Fire on October 12, 2017 near Calistoga, California. At least thirty one people have died in wildfires that have burned tens of thousands of acres and destroyed over 3,500 homes and businesses in several Northern California counties. (Photo by Justin Sullivan/Getty Images)Photo: Justin Sullivan/Getty Images

45of65A firefighter carries a water hose to put out a fire during along the Highway 29 Friday, Oct. 13, 2017, near Calistoga, Calif. Firefighters gained some ground on a blaze burning in the heart of California's wine country but face another tough day ahead with low humidity and high winds expected to return. (AP Photo/Jae C. Hong)Photo: Jae C. Hong, Associated Press

46of65Firefighters watch from their fire trucks as wildfires continue to burn Thursday, Oct. 12, 2017, near Calistoga, Calif. Some of the state's most historic tourist sites, including Sonoma city and Calistoga in Napa Valley, were ghost towns populated only by fire crews trying to stop the advancing infernos. (AP Photo/Jae C. Hong)Photo: Jae C. Hong, Associated Press

47of65The Puerta la Cruz female inmate firefighter crew clears vegetation near homes in Dry Creek Canyon to try to save them as the Partrick Fire approaches on October 12, 2017 west of Napa, California. Inmate hand crews work under the supervision of Cal Fire, which refers to them as firefighters rather than prisoners because they perform the same job as the elite Hot Shot firefighter crews. Thousands of homes have burned, at least 31 people confirmed killed with hundreds still missing as California wildfires continue to spread out of control. (Photo by David McNew/Getty Images)Photo: David McNew/Getty Images

48of65Firefighters try to extinguish a house fire during the Tubbs Fire on October 12, 2017 near Calistoga, California. At least thirty one people have died in wildfires that have burned tens of thousands of acres and destroyed over 3,500 homes and businesses in several Northern California counties. (Photo by Justin Sullivan/Getty Images)Photo: Justin Sullivan/Getty Images

49of65Neighbors gather along Old Vineyard Road to watch the progress of the fire as the Partrick Fire continue to burn slowly east of Sonoma, Calif., on Thursday, October 12, 2017. The Napa and Sonoma valleys continue to be under threat from several fires not yet under control and growing fears that strong winds might worsen the situation.Photo: Carlos Avila Gonzalez, The Chronicle

50of65Flames erupt off Lovall Valley Road as the Partrick Fire continue to burn slowly east of Sonoma, Calif., on Thursday, October 12, 2017. The Napa and Sonoma valleys continue to be under threat from several fires not yet under control and growing fears that strong winds might worsen the situation.Photo: Carlos Avila Gonzalez, The Chronicle

51of65Homes leveled by the Tubbs fire line a neighborhood of Santa Rosa, Calif., on Wednesday, Oct. 11, 2017.Photo: Noah Berger, Special to The Chronicle

52of65A Cal Fire helicopter drops water on a smoldering area as the Partrick Fire continue to burn slowly east of Sonoma, Calif., on Thursday, October 12, 2017. The Napa and Sonoma valleys continue to be under threat from several fires not yet under control and growing fears that strong winds might worsen the situation.Photo: Carlos Avila Gonzalez, The Chronicle

53of65Dr. Emily Putt tries to calm an anxious horse as her friend retrieves tranquilizers to administer to it as they rescue two horses for an evacuation Oct. 11, 2017 in Sonoma, Calif. Putt has been working with her friends since Monday, when the fires broke out, to rescue animals that are being threatened by the fires.Photo: Leah Millis, The Chronicle

54of65A grove of trees near Trinity Road glows as it burns near a vineyard after a mandatory evacuation was called in the area of Glen Ellen, Calif., on Wednesday, October 11, 2017. The Napa and Sonoma valleys continue to be under threat from several fires not yet under control and growing fears that strong winds might worsen the situation.Photo: Carlos Avila Gonzalez, The Chronicle

55of65Two police officers direct a motorist to return at a road closure at Madrone Road after a mandatory evacuation was called in the area of Glen Ellen, Calif., on Wednesday, October 11, 2017. The Napa and Sonoma valleys continue to be under threat from several fires not yet under control and growing fears that strong winds might worsen the situation.Photo: Carlos Avila Gonzalez, The Chronicle

57of65John Gilson and Derek DeBendetti (left to right) try to put out a hot spot at Cardinal Newman High School in Santa Rosa, Ca. on Wednesday, October 11, 2017. Gilson is Dean of Students at Cardinal Newman as well as the Varsity Women's Soccer coach and Freshman Baseball coach. DeBanedetti is a math teacher at Cardinal Newman and the Varisty Baseball Coach. The school suffered major damages in the Tubbs Fire.Photo: Alex Washburn, The Chronicle

58of65A firefighter works in a devastated neighborhood as an American flag flies from the remains of a home on Willowview Ct. off Skyview Dr. Oct. 11, 2017 in Santa Rosa, Calif.Photo: Leah Millis, The Chronicle

59of65Karen Balestieri and Heidi Facciano (left to right) marvel at a pond of live koi fish which survived the Tubbs fire in the neighborhood referred to by locals as 'old fountaingrove' in Santa Rosa, Ca. on Wednesday, October 11, 2017.Photo: Alex Washburn, The Chronicle

60of65Burned out and collapsed house along Mt Veeder Rd after flames from the Nuns fire moved through the Mt Veeder area in Napa, California, USA 11 Oct 2017.Photo: Peter DaSilva, Special to The Chronicle

61of65Fire fighters clear a downed tree from across Mt Veeder Rd after flames from the Nuns fire moved through the Mt Veeder area in Napa, California, USA 11 Oct 2017.Photo: Peter DaSilva, Special to The Chronicle

62of65Workers move historic items from the Sonoma Barracks Oct. 11, 2017 in downtown Sonoma, Calif. California State Parks decided to move the items from the Barracks and Mission San Francisco Solano as a precautionary measure as fires burned beyond the town.Photo: Leah Millis, The Chronicle

63of65A primary school classroom at St. Rose School is seen with damages caused by the Tubbs fire in Santa Rosa, Ca. on Wednesday, October 11, 2017.Photo: Alex Washburn, The Chronicle

64of65A firefighter works to control a fire near a bulldozer line created behind homes along Bennett Valley Road as he and other firefighters monitor it 's progress on Wednesday, October 11, 2017 in Santa Rosa, Calif.Photo: Lea Suzuki, The Chronicle

65of65Fire fighting incident commanders plan for changing weather conditions along Mt Veeder road as flames from the Nuns fire continue to burn in the Mt Veeder area in Napa, California, USA 11 Oct 2017.Photo: Peter DaSilva, Special to The Chronicle

The catastrophic fires that have ravaged Wine Country this week may be unprecedented in their toll, but they’re only the latest in a wave of infernos that have blasted through the hills and valleys north of San Francisco in recent years. And the trend is likely to worsen.

As temperatures climb across the West and as a sprawling Bay Area expands development into increasingly rural reaches, Northern California is becoming more akin to Southern California, where warm weather and people staking trophy homes along far-flung cliffs and canyons have set the stage for chronic burning, fire experts say.

“I can’t imagine how there isn’t going to be more of this in the future,” said Hugh Safford, an ecologist for the U.S. Forest Service’s Pacific Southwest Region. “It’s shocking what’s happened, but it really isn’t necessarily all that surprising.”

In the past few years, the north state’s coastal mountains have witnessed several devastating burns, much in line with what the southern coast has long endured. In 2015, the Valley Fire that spread into Lake, Sonoma and Napa counties destroyed nearly 1,300 homes and killed four people, and the following year a blaze wiped out the heart of the Lake County town of Lower Lake.

The most destructive of this week’s wildfires are within an hour’s drive south of Lower Lake, but they swept into areas much more populated, such as the north edge of Santa Rosa, intensifying the impact.

“That part of the state over the past four years ... has had an endless series of unrelenting fires,” Safford said. “It’s typical of the coast ranges, when you get to Santa Barbara and south, which are dry and hence more flammable. But this is really a new thing here. I think that Lake County may be the next frontier of Southern California as it moves north.”

While fall has always been the most perilous season for Northern California wildfires, as offshore winds pick up and the trees and shrubs reach their driest points after the warm summer months, a number of the underlying forces have changed in the past decade or two.

The most obvious is temperature, which has risen globally as a result of human-induced greenhouse gas emissions. This summer marked California’s hottest in recorded history. San Francisco reached an all-time high of 106 degrees in September, continuing a trajectory that’s put the Bay Area more on par with balmier Southern California.

The milder weather means that vegetation is dryer and more combustible and that the fire season runs longer, perhaps eventually becoming a year-round affair as it is in Southern California.

“As long as you have stuff to burn, warming temperatures increase the likelihood that stuff is going to burn,” said Park Williams, a bioclimatologist and research professor at Columbia University’s Lamont-Doherty Earth Observatory in New York. “Climate is certainly driving the trends that we’re seeing in fire across the West.”

A study published last year by Williams suggests that as much as half the burning of forest land in Western states since the 1980s is due to global warming.

Research also shows that extremes of weather both wet and dry — another product of climate change — are pushing more powerful blazes. Climate experts point with alarm to the way this year’s extraordinarily rainy winter in California, which created a bumper crop of brush and grass, gave way swiftly to record heat that dried out the wildlands and provided copious fuel to burn.

“This is the recipe for bigger fires,” Williams said. “Most models agree that the frequency of extremely wet years will increase, and that happens at the same time that all models show things getting warmer.”

The same models explain the deadly string of hurricanes that battered parts of the U.S. and the Caribbean over the past few months. And they may explain recent landslides and drought in Africa, and threatening tsunamis in Central America.

West Coast scientists are also investigating whether the warming planet is intensifying the hot offshore winds that have driven this week’s Wine Country fires, commonly called Diablo winds.

At the same time, researchers are looking into whether climate change is tied to warmer evening temperatures, which have allowed fires like the ones in Napa and Sonoma counties to burn overnight rather than begin to cool. The worst damage in Sonoma County occurred between midnight and dawn on Monday.

While climate has created a playing field more conducive to furious and frequent fires, the root cause of the burns remains, almost exclusively, human failing. Northern California’s coastal mountains don’t see much lightning, and before the hills were settled, fire was relatively uncommon here. Today, there’s no shortage of ignition sources, whether downed power lines, automobile tailpipes or cigarette butts.

“People want to live out in the woods, and this is always a real and present danger,” said Safford of the Forest Service. “These fires should probably be a wake-up call to think more about human habitation and how we deal with that.”

The growth of fires will likely put increasing pressure on state and federal firefighting budgets. Just three months into the current fiscal year, the California Department of Forestry and Fire Protection had spent $258 million of its roughly $430 million annual emergency fund — and that was before the Wine Country fires broke out.

“This week’s fires alone are going to chew up quite a bit of what is left,” said Cal Fire spokeswoman Lynne Tolmachoff. “And we’re not done with fire season. We don’t have any precipitation showing up in our forecasts. And then there’s the fires in May and June next year.”

While it’s still early in the budget year, Cal Fire’s outlay is nearly on pace with the record $547 million expended in 2015-16, an amount that required the state to tap other funding streams as well as federal aid. The amount of emergency money spent annually by Cal Fire in the past five years is more than double what it was a decade ago.

Through Sunday, before wide swaths of Northern California turned into a disaster zone, wildfires had blackened about 850,000 acres across the state, nearly 70 percent above the five-year average for the date.

Kurtis Alexander is a general assignment reporter for The San Francisco Chronicle, frequently writing about water, wildfire, climate and the American West. His recent work has focused on the impacts of drought, the widening rural-urban divide and state and federal environmental policy.

Before joining the Chronicle, Alexander worked as a freelance writer and as a staff reporter for several media organizations, including The Fresno Bee and Bay Area News Group, writing about government, politics and the environment.